Quarterly report pursuant to Section 13 or 15(d)

Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (AO LTIP Units (Appreciation-Only LTIP Units)) (Narrative) (Details)

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Mack-Cali Realty Corporation Stockholders' Equity And Mack-Cali Realty, L.P.'s Partners' Capital (AO LTIP Units (Appreciation-Only LTIP Units)) (Narrative) (Details) - USD ($)
3 Months Ended
Jun. 05, 2015
Mar. 31, 2020
Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares granted 800,000    
Share price $ 17.31    
Exercisable period   10 years  
Common stock trading days   30 days  
Common stock trade share price $ 25.00    
Stock options expense   $ 0 $ 0
AO LTIP Units Award [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share price   $ 21.46  
Exercisable period   10 years  
Share price - weighted average fair value of options granted   $ 3.98  
Total unrecognized compensation cost   $ 1,800,000  
Total unrecognized compensation cost, period of recognition   2 years 10 months 24 days  
Stock options expense   $ 155,000 $ 32,000
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares granted   625,000  
Income allocation   10.00%  
Percent of cash distribution   10.00%  
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member] | Tranche One [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares to be vested and exercisable   250,000  
Common stock trading days   30 days  
Common stock trade share price   $ 25.00  
Common stock expiration date   Mar. 13, 2023  
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member] | Tranche Two [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares to be vested and exercisable   250,000  
Common stock trading days   30 days  
Common stock trade share price   $ 28.00  
AO LTIP Units Award [Member] | Messr DeMarco, CEO [Member] | Tranche Three [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares to be vested and exercisable   125,000  
Common stock trading days   30 days  
Common stock trade share price   $ 31.00